The incident occurred at a stop sign where I was waiting behind one other vehicle. The vehicle ahead of me accelerated from the stop sign to turn into traffic, but abruptly slammed on their brakes. I had began accelerating up to the stop sign and was unable to stop before impacting the car in front of me. As soon as I saw the vehicle was braking, I immediately slammed on the brake pedal. Braking did not immediately occur. My wife said she was afraid that I had slammed the gas pedal because she could hear my foot hit the brake pedal and neither of us felt any braking. The Nissan Leaf was in Eco Mode and ePedal at the time of the incident. I believe that the transition from regenerative braking to mechanical braking delayed the stopping of my vehicle. We were lucky that this happened in a very low consequence situation, but if this happened with a pedestrian or at a higher speed where emergency braking is required, this delay in braking could be dire. In addition, this vehicle is equipped with automatic emergency braking. I have heard this feature go off before in this specific car when a car is braking faster than I am. In this case, the alarm and assisted braking did not go off, despite a car stopping within extremely close proximity.